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6365ba64b4
KVM_HC_CLOCK_PAIRING currently fails inside SEV-SNP guests because the guest passes an address to static data to the host. In confidential computing the host can't access arbitrary guest memory so handling the hypercall runs into an "rmpfault". To make the hypercall work, the guest needs to explicitly mark the memory as decrypted. Do that in kvm_arch_ptp_init(), but retain the previous behavior for non-confidential guests to save us from having to allocate memory. Add a new arch-specific function (kvm_arch_ptp_exit()) to free the allocation and mark the memory as encrypted again. Signed-off-by: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com> Link: https://lore.kernel.org/r/20230308150531.477741-1-jpiotrowski@linux.microsoft.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
129 lines
2.7 KiB
C
129 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Virtual PTP 1588 clock for use with KVM guests
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*
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* Copyright (C) 2017 Red Hat Inc.
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*/
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#include <linux/device.h>
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#include <linux/kernel.h>
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#include <asm/pvclock.h>
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#include <asm/kvmclock.h>
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#include <linux/module.h>
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#include <uapi/asm/kvm_para.h>
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#include <uapi/linux/kvm_para.h>
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#include <linux/ptp_clock_kernel.h>
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#include <linux/ptp_kvm.h>
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#include <linux/set_memory.h>
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static phys_addr_t clock_pair_gpa;
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static struct kvm_clock_pairing clock_pair_glbl;
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static struct kvm_clock_pairing *clock_pair;
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int kvm_arch_ptp_init(void)
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{
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struct page *p;
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long ret;
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if (!kvm_para_available())
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return -ENODEV;
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if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
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p = alloc_page(GFP_KERNEL | __GFP_ZERO);
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if (!p)
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return -ENOMEM;
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clock_pair = page_address(p);
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ret = set_memory_decrypted((unsigned long)clock_pair, 1);
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if (ret) {
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__free_page(p);
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clock_pair = NULL;
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goto nofree;
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}
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} else {
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clock_pair = &clock_pair_glbl;
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}
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clock_pair_gpa = slow_virt_to_phys(clock_pair);
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if (!pvclock_get_pvti_cpu0_va()) {
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ret = -ENODEV;
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goto err;
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}
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ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
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KVM_CLOCK_PAIRING_WALLCLOCK);
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if (ret == -KVM_ENOSYS) {
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ret = -ENODEV;
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goto err;
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}
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return ret;
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err:
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kvm_arch_ptp_exit();
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nofree:
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return ret;
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}
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void kvm_arch_ptp_exit(void)
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{
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if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
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WARN_ON(set_memory_encrypted((unsigned long)clock_pair, 1));
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free_page((unsigned long)clock_pair);
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clock_pair = NULL;
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}
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}
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int kvm_arch_ptp_get_clock(struct timespec64 *ts)
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{
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long ret;
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ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
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clock_pair_gpa,
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KVM_CLOCK_PAIRING_WALLCLOCK);
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if (ret != 0) {
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pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
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return -EOPNOTSUPP;
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}
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ts->tv_sec = clock_pair->sec;
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ts->tv_nsec = clock_pair->nsec;
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return 0;
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}
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int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
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struct clocksource **cs)
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{
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struct pvclock_vcpu_time_info *src;
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unsigned int version;
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long ret;
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src = this_cpu_pvti();
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do {
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/*
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* We are using a TSC value read in the hosts
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* kvm_hc_clock_pairing handling.
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* So any changes to tsc_to_system_mul
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* and tsc_shift or any other pvclock
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* data invalidate that measurement.
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*/
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version = pvclock_read_begin(src);
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ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
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clock_pair_gpa,
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KVM_CLOCK_PAIRING_WALLCLOCK);
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if (ret != 0) {
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pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
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return -EOPNOTSUPP;
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}
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tspec->tv_sec = clock_pair->sec;
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tspec->tv_nsec = clock_pair->nsec;
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*cycle = __pvclock_read_cycles(src, clock_pair->tsc);
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} while (pvclock_read_retry(src, version));
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*cs = &kvm_clock;
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return 0;
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}
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