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x86/sev-es: Handle RDTSC(P) Events

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Implement a handler for #VC exceptions caused by RDTSC and RDTSCP
instructions. Also make it available in the pre-decompression stage
because the KASLR code uses RDTSC/RDTSCP to gather entropy and some
hypervisors intercept these instructions.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: - Adapt to #VC handling infrastructure
                   - Make it available early ]
Co-developed-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-55-joro@8bytes.org
This commit is contained in:
Tom Lendacky 2020-09-07 15:15:55 +02:00 committed by Borislav Petkov
parent a14a92fc4b
commit 4711e7acaa
3 changed files with 31 additions and 0 deletions
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4
arch/x86/boot/compressed/sev-es.c
View file

@ -181,6 +181,10 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
goto finish;
switch (exit_code) {
case SVM_EXIT_RDTSC:
case SVM_EXIT_RDTSCP:
result = vc_handle_rdtsc(boot_ghcb, &ctxt, exit_code);
break;
case SVM_EXIT_IOIO:
result = vc_handle_ioio(boot_ghcb, &ctxt);
break;

23
arch/x86/kernel/sev-es-shared.c
View file

@ -467,3 +467,26 @@ static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
return ES_OK;
}
static enum es_result vc_handle_rdtsc(struct ghcb *ghcb,
struct es_em_ctxt *ctxt,
unsigned long exit_code)
{
bool rdtscp = (exit_code == SVM_EXIT_RDTSCP);
enum es_result ret;
ret = sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, 0, 0);
if (ret != ES_OK)
return ret;
if (!(ghcb_rax_is_valid(ghcb) && ghcb_rdx_is_valid(ghcb) &&
(!rdtscp || ghcb_rcx_is_valid(ghcb))))
return ES_VMM_ERROR;
ctxt->regs->ax = ghcb->save.rax;
ctxt->regs->dx = ghcb->save.rdx;
if (rdtscp)
ctxt->regs->cx = ghcb->save.rcx;
return ES_OK;
}

4
arch/x86/kernel/sev-es.c
View file

@ -866,6 +866,10 @@ static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
case SVM_EXIT_WRITE_DR7:
result = vc_handle_dr7_write(ghcb, ctxt);
break;
case SVM_EXIT_RDTSC:
case SVM_EXIT_RDTSCP:
result = vc_handle_rdtsc(ghcb, ctxt, exit_code);
break;
case SVM_EXIT_CPUID:
result = vc_handle_cpuid(ghcb, ctxt);
break;