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x86/sev-es: Add CPUID handling to #VC handler 

Handle #VC exceptions caused by CPUID instructions. These happen in
early boot code when the KASLR code checks for RDTSC.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: Adapt to #VC handling framework ]
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/20200907131613.12703-28-joro@8bytes.org
This commit is contained in:
Tom Lendacky 2020-09-07 15:15:28 +02:00 committed by Borislav Petkov
parent 1b4fb8545f
commit a7de15d489
2 changed files with 39 additions and 0 deletions
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4
arch/x86/boot/compressed/sev-es.c
View File

@ -16,6 +16,7 @@
#include <asm/trapnr.h>
#include <asm/trap_pf.h>
#include <asm/msr-index.h>
#include <asm/fpu/xcr.h>
#include <asm/ptrace.h>
#include <asm/svm.h>
@ -183,6 +184,9 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
case SVM_EXIT_IOIO:
result = vc_handle_ioio(boot_ghcb, &ctxt);
break;
case SVM_EXIT_CPUID:
result = vc_handle_cpuid(boot_ghcb, &ctxt);
break;
default:
result = ES_UNSUPPORTED;
break;

35
arch/x86/kernel/sev-es-shared.c
View File

@ -432,3 +432,38 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
return ret;
}
static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
struct es_em_ctxt *ctxt)
{
struct pt_regs *regs = ctxt->regs;
u32 cr4 = native_read_cr4();
enum es_result ret;
ghcb_set_rax(ghcb, regs->ax);
ghcb_set_rcx(ghcb, regs->cx);
if (cr4 & X86_CR4_OSXSAVE)
/* Safe to read xcr0 */
ghcb_set_xcr0(ghcb, xgetbv(XCR_XFEATURE_ENABLED_MASK));
else
/* xgetbv will cause #GP - use reset value for xcr0 */
ghcb_set_xcr0(ghcb, 1);
ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_CPUID, 0, 0);
if (ret != ES_OK)
return ret;
if (!(ghcb_rax_is_valid(ghcb) &&
ghcb_rbx_is_valid(ghcb) &&
ghcb_rcx_is_valid(ghcb) &&
ghcb_rdx_is_valid(ghcb)))
return ES_VMM_ERROR;
regs->ax = ghcb->save.rax;
regs->bx = ghcb->save.rbx;
regs->cx = ghcb->save.rcx;
regs->dx = ghcb->save.rdx;
return ES_OK;
}