Commit 4711e7ac authored by Tom Lendacky's avatar Tom Lendacky Committed by Borislav Petkov
Browse files

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



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: default avatarTom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: - Adapt to #VC handling infrastructure
                   - Make it available early ]
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/20200907131613.12703-55-joro@8bytes.org
parent a14a92fc

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

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

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

+23 −0
Original line number Diff line number Diff line
@@ -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;

}

arch/x86/kernel/sev-es.c

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