Commit a7de15d4 authored by Tom Lendacky's avatar Tom Lendacky Committed by Borislav Petkov
Browse files

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: default avatarTom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: Adapt to #VC handling framework ]
Co-developed-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-28-joro@8bytes.org
parent 1b4fb854

arch/x86/boot/compressed/sev-es.c

+4 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/kernel/sev-es-shared.c

+35 −0
Original line number Diff line number Diff line
@@ -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;

}

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