On Wed, Jul 21, 2021, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@xxxxxxx>
>
> Handle CLFLUSH instruction to MMIO memory in the #VC handler. The
^
|- emulated
> instruction is ignored by the handler, as the Hypervisor is
> responsible for cache management of emulated MMIO memory.
>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> arch/x86/kernel/sev-shared.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index a7a0793c4f98..682fa202444f 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -632,6 +632,15 @@ static enum es_result vc_handle_mmio_twobyte_ops(struct ghcb *ghcb,
> long *reg_data;
>
> switch (insn->opcode.bytes[1]) {
> + /* CLFLUSH */
> + case 0xae:
> + /*
> + * Ignore CLFLUSHes - those go to emulated MMIO anyway and the
> + * hypervisor is responsible for cache management.
This wording can be misread as "the hypervisor is responsible for _all_ cache
management". Maybe just:
/*
* Ignore CLFLUSHes - the hyperivsor is responsible for cache
* management of emulated MMIO.
*/
Side topic, out of curisoity, what's mapping/accessing emulated MMIO as non-UC?
> + */
> + ret = ES_OK;
> + break;
> +
> /* MMIO Read w/ zero-extension */
> case 0xb6:
> bytes = 1;
> --
> 2.31.1
>
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