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KVM: arm64: pkvm: Add support for fragmented FF-A descriptors

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FF-A memory descriptors may need to be sent in fragments when they don't
fit in the mailboxes. Doing so involves using the FRAG_TX and FRAG_RX
primitives defined in the FF-A protocol.

Add support in the pKVM FF-A relayer for fragmented descriptors by
monitoring outgoing FRAG_TX transactions and by buffering large
descriptors on the reclaim path.

Co-developed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230523101828.7328-11-will@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Quentin Perret 2023-05-23 11:18:27 +01:00 committed by Oliver Upton
parent 20936cd114
commit 0a9f15fd56
2 changed files with 162 additions and 25 deletions
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17
arch/arm64/include/asm/kvm_pkvm.h
View file

@ -6,7 +6,9 @@
#ifndef __ARM64_KVM_PKVM_H__
#define __ARM64_KVM_PKVM_H__
#include <linux/arm_ffa.h>
#include <linux/memblock.h>
#include <linux/scatterlist.h>
#include <asm/kvm_pgtable.h>
/* Maximum number of VMs that can co-exist under pKVM. */
@ -110,8 +112,19 @@ static inline unsigned long host_s2_pgtable_pages(void)
static inline unsigned long hyp_ffa_proxy_pages(void)
{
/* A page each for the hypervisor's RX and TX mailboxes. */
return 2 * KVM_FFA_MBOX_NR_PAGES;
size_t desc_max;
/*
* The hypervisor FFA proxy needs enough memory to buffer a fragmented
* descriptor returned from EL3 in response to a RETRIEVE_REQ call.
*/
desc_max = sizeof(struct ffa_mem_region) +
sizeof(struct ffa_mem_region_attributes) +
sizeof(struct ffa_composite_mem_region) +
SG_MAX_SEGMENTS * sizeof(struct ffa_mem_region_addr_range);
/* Plus a page each for the hypervisor's RX and TX mailboxes. */
return (2 * KVM_FFA_MBOX_NR_PAGES) + DIV_ROUND_UP(desc_max, PAGE_SIZE);
}
#endif /* __ARM64_KVM_PKVM_H__ */

170
arch/arm64/kvm/hyp/nvhe/ffa.c
View file

@ -42,6 +42,18 @@
*/
#define HOST_FFA_ID 0
/*
* A buffer to hold the maximum descriptor size we can see from the host,
* which is required when the SPMD returns a fragmented FFA_MEM_RETRIEVE_RESP
* when resolving the handle on the reclaim path.
*/
struct kvm_ffa_descriptor_buffer {
void *buf;
size_t len;
};
static struct kvm_ffa_descriptor_buffer ffa_desc_buf;
struct kvm_ffa_buffers {
hyp_spinlock_t lock;
void *tx;
@ -122,6 +134,24 @@ static int ffa_unmap_hyp_buffers(void)
return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
}
static void ffa_mem_frag_tx(struct arm_smccc_res *res, u32 handle_lo,
u32 handle_hi, u32 fraglen, u32 endpoint_id)
{
arm_smccc_1_1_smc(FFA_MEM_FRAG_TX,
handle_lo, handle_hi, fraglen, endpoint_id,
0, 0, 0,
res);
}
static void ffa_mem_frag_rx(struct arm_smccc_res *res, u32 handle_lo,
u32 handle_hi, u32 fragoff)
{
arm_smccc_1_1_smc(FFA_MEM_FRAG_RX,
handle_lo, handle_hi, fragoff, HOST_FFA_ID,
0, 0, 0,
res);
}
static void ffa_mem_xfer(struct arm_smccc_res *res, u64 func_id, u32 len,
u32 fraglen)
{
@ -327,6 +357,64 @@ static int ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
return ret;
}
static void do_ffa_mem_frag_tx(struct arm_smccc_res *res,
struct kvm_cpu_context *ctxt)
{
DECLARE_REG(u32, handle_lo, ctxt, 1);
DECLARE_REG(u32, handle_hi, ctxt, 2);
DECLARE_REG(u32, fraglen, ctxt, 3);
DECLARE_REG(u32, endpoint_id, ctxt, 4);
struct ffa_mem_region_addr_range *buf;
int ret = FFA_RET_INVALID_PARAMETERS;
u32 nr_ranges;
if (fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)
goto out;
if (fraglen % sizeof(*buf))
goto out;
hyp_spin_lock(&host_buffers.lock);
if (!host_buffers.tx)
goto out_unlock;
buf = hyp_buffers.tx;
memcpy(buf, host_buffers.tx, fraglen);
nr_ranges = fraglen / sizeof(*buf);
ret = ffa_host_share_ranges(buf, nr_ranges);
if (ret) {
/*
* We're effectively aborting the transaction, so we need
* to restore the global state back to what it was prior to
* transmission of the first fragment.
*/
ffa_mem_reclaim(res, handle_lo, handle_hi, 0);
WARN_ON(res->a0 != FFA_SUCCESS);
goto out_unlock;
}
ffa_mem_frag_tx(res, handle_lo, handle_hi, fraglen, endpoint_id);
if (res->a0 != FFA_SUCCESS && res->a0 != FFA_MEM_FRAG_RX)
WARN_ON(ffa_host_unshare_ranges(buf, nr_ranges));
out_unlock:
hyp_spin_unlock(&host_buffers.lock);
out:
if (ret)
ffa_to_smccc_res(res, ret);
/*
* If for any reason this did not succeed, we're in trouble as we have
* now lost the content of the previous fragments and we can't rollback
* the host stage-2 changes. The pages previously marked as shared will
* remain stuck in that state forever, hence preventing the host from
* sharing/donating them again and may possibly lead to subsequent
* failures, but this will not compromise confidentiality.
*/
return;
}
static __always_inline void do_ffa_mem_xfer(const u64 func_id,
struct arm_smccc_res *res,
struct kvm_cpu_context *ctxt)
@ -337,8 +425,8 @@ static __always_inline void do_ffa_mem_xfer(const u64 func_id,
DECLARE_REG(u32, npages_mbz, ctxt, 4);
struct ffa_composite_mem_region *reg;
struct ffa_mem_region *buf;
u32 offset, nr_ranges;
int ret = 0;
u32 offset;
BUILD_BUG_ON(func_id != FFA_FN64_MEM_SHARE &&
func_id != FFA_FN64_MEM_LEND);
@ -349,11 +437,6 @@ static __always_inline void do_ffa_mem_xfer(const u64 func_id,
goto out;
}
if (fraglen < len) {
ret = FFA_RET_ABORTED;
goto out;
}
if (fraglen < sizeof(struct ffa_mem_region) +
sizeof(struct ffa_mem_region_attributes)) {
ret = FFA_RET_INVALID_PARAMETERS;
@ -381,21 +464,26 @@ static __always_inline void do_ffa_mem_xfer(const u64 func_id,
}
reg = (void *)buf + offset;
if (fraglen < offset + sizeof(struct ffa_composite_mem_region) +
reg->addr_range_cnt *
sizeof(struct ffa_mem_region_addr_range)) {
nr_ranges = ((void *)buf + fraglen) - (void *)reg->constituents;
if (nr_ranges % sizeof(reg->constituents[0])) {
ret = FFA_RET_INVALID_PARAMETERS;
goto out_unlock;
}
ret = ffa_host_share_ranges(reg->constituents, reg->addr_range_cnt);
nr_ranges /= sizeof(reg->constituents[0]);
ret = ffa_host_share_ranges(reg->constituents, nr_ranges);
if (ret)
goto out_unlock;
ffa_mem_xfer(res, func_id, len, fraglen);
if (res->a0 != FFA_SUCCESS) {
WARN_ON(ffa_host_unshare_ranges(reg->constituents,
reg->addr_range_cnt));
if (fraglen != len) {
if (res->a0 != FFA_MEM_FRAG_RX)
goto err_unshare;
if (res->a3 != fraglen)
goto err_unshare;
} else if (res->a0 != FFA_SUCCESS) {
goto err_unshare;
}
out_unlock:
@ -404,6 +492,10 @@ static __always_inline void do_ffa_mem_xfer(const u64 func_id,
if (ret)
ffa_to_smccc_res(res, ret);
return;
err_unshare:
WARN_ON(ffa_host_unshare_ranges(reg->constituents, nr_ranges));
goto out_unlock;
}
static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
@ -413,9 +505,9 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
DECLARE_REG(u32, handle_hi, ctxt, 2);
DECLARE_REG(u32, flags, ctxt, 3);
struct ffa_composite_mem_region *reg;
u32 offset, len, fraglen, fragoff;
struct ffa_mem_region *buf;
int ret = 0;
u32 offset;
u64 handle;
handle = PACK_HANDLE(handle_lo, handle_hi);
@ -433,11 +525,8 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
if (res->a0 != FFA_MEM_RETRIEVE_RESP)
goto out_unlock;
/* Check for fragmentation */
if (res->a1 != res->a2) {
ret = FFA_RET_ABORTED;
goto out_unlock;
}
len = res->a1;
fraglen = res->a2;
offset = buf->ep_mem_access[0].composite_off;
/*
@ -445,16 +534,36 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
* check that we end up with something that doesn't look _completely_
* bogus.
*/
if (WARN_ON(offset > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) {
if (WARN_ON(offset > len ||
fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) {
ret = FFA_RET_ABORTED;
goto out_unlock;
}
reg = (void *)buf + offset;
if (len > ffa_desc_buf.len) {
ret = FFA_RET_NO_MEMORY;
goto out_unlock;
}
buf = ffa_desc_buf.buf;
memcpy(buf, hyp_buffers.rx, fraglen);
for (fragoff = fraglen; fragoff < len; fragoff += fraglen) {
ffa_mem_frag_rx(res, handle_lo, handle_hi, fragoff);
if (res->a0 != FFA_MEM_FRAG_TX) {
ret = FFA_RET_INVALID_PARAMETERS;
goto out_unlock;
}
fraglen = res->a3;
memcpy((void *)buf + fragoff, hyp_buffers.rx, fraglen);
}
ffa_mem_reclaim(res, handle_lo, handle_hi, flags);
if (res->a0 != FFA_SUCCESS)
goto out_unlock;
reg = (void *)buf + offset;
/* If the SPMD was happy, then we should be too. */
WARN_ON(ffa_host_unshare_ranges(reg->constituents,
reg->addr_range_cnt));
@ -569,6 +678,9 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
case FFA_FN64_MEM_LEND:
do_ffa_mem_xfer(FFA_FN64_MEM_LEND, &res, host_ctxt);
goto out_handled;
case FFA_MEM_FRAG_TX:
do_ffa_mem_frag_tx(&res, host_ctxt);
goto out_handled;
}
if (ffa_call_supported(func_id))
@ -584,6 +696,7 @@ int hyp_ffa_init(void *pages)
{
struct arm_smccc_res res;
size_t min_rxtx_sz;
void *tx, *rx;
if (kvm_host_psci_config.smccc_version < ARM_SMCCC_VERSION_1_2)
return 0;
@ -624,10 +737,21 @@ int hyp_ffa_init(void *pages)
if (min_rxtx_sz > PAGE_SIZE)
return -EOPNOTSUPP;
tx = pages;
pages += KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE;
rx = pages;
pages += KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE;
ffa_desc_buf = (struct kvm_ffa_descriptor_buffer) {
.buf = pages,
.len = PAGE_SIZE *
(hyp_ffa_proxy_pages() - (2 * KVM_FFA_MBOX_NR_PAGES)),
};
hyp_buffers = (struct kvm_ffa_buffers) {
.lock = __HYP_SPIN_LOCK_UNLOCKED,
.tx = pages,
.rx = pages + (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE),
.tx = tx,
.rx = rx,
};
host_buffers = (struct kvm_ffa_buffers) {