[PATCH v3 09/10] x86/sev: Handle CLFLUSH MMIO events

Joerg Roedel
2022-01-27T10:11:41Z

Handle CLFLUSH instruction to MMIO memory in the #VC handler. The
instruction is ignored by the handler, as the Hypervisor is
responsible for cache management of emulated MMIO memory.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/include/asm/insn-eval.h | 1 +
arch/x86/kernel/sev-shared.c | 3 +++
arch/x86/lib/insn-eval-shared.c | 7 +++++++
3 files changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index f07faa61c7f3..c3eb753a912b 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -40,6 +40,7 @@ enum mmio_type {
MMIO_READ_ZERO_EXTEND,
MMIO_READ_SIGN_EXTEND,
MMIO_MOVS,
+ MMIO_IGNORE,
};

enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes);
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index b12fb063a30e..1aa33509c7b5 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -698,6 +698,9 @@ static enum es_result vc_handle_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
if (mmio == MMIO_DECODE_FAILED)
return ES_DECODE_FAILED;

+ if (mmio == MMIO_IGNORE)
+ return ES_OK;
+
if (mmio != MMIO_WRITE_IMM && mmio != MMIO_MOVS) {
reg_data = insn_get_modrm_reg_ptr(insn, ctxt->regs);
if (!reg_data)
diff --git a/arch/x86/lib/insn-eval-shared.c b/arch/x86/lib/insn-eval-shared.c
index ec310b5e6cd5..ddec72fccdd2 100644
--- a/arch/x86/lib/insn-eval-shared.c
+++ b/arch/x86/lib/insn-eval-shared.c
@@ -898,6 +898,13 @@ enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes)
*bytes = 2;
type = MMIO_READ_SIGN_EXTEND;
break;
+ case 0xae: /* CLFLUSH */
+ /*
+ * Ignore CLFLUSHes - those go to emulated MMIO anyway and the
+ * hypervisor is responsible for cache management.
+ */
+ type = MMIO_IGNORE;
+ break;
}
break;
}
--
2.34.1