Re: [PATCH 40/70] x86/sev-es: Setup per-cpu GHCBs for the runtime handler

[Mike Stunes]

On Mar 19, 2020, at 2:13 AM, Joerg Roedel <joro@xxxxxxxxxx> wrote:
> 
> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
> 
> The runtime handler needs a GHCB per CPU. Set them up and map them
> unencrypted.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> arch/x86/include/asm/mem_encrypt.h |  2 ++
> arch/x86/kernel/sev-es.c           | 28 +++++++++++++++++++++++++++-
> arch/x86/kernel/traps.c            |  3 +++
> 3 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
> index c17980e8db78..4bf5286310a0 100644
> --- a/arch/x86/kernel/sev-es.c
> +++ b/arch/x86/kernel/sev-es.c
> @@ -197,6 +203,26 @@ static bool __init sev_es_setup_ghcb(void)
> 	return true;
> }
> 
> +void sev_es_init_ghcbs(void)
> +{
> +	int cpu;
> +
> +	if (!sev_es_active())
> +		return;
> +
> +	/* Allocate GHCB pages */
> +	ghcb_page = __alloc_percpu(sizeof(struct ghcb), PAGE_SIZE);
> +
> +	/* Initialize per-cpu GHCB pages */
> +	for_each_possible_cpu(cpu) {
> +		struct ghcb *ghcb = (struct ghcb *)per_cpu_ptr(ghcb_page, cpu);
> +
> +		set_memory_decrypted((unsigned long)ghcb,
> +				     sizeof(*ghcb) >> PAGE_SHIFT);
> +		memset(ghcb, 0, sizeof(*ghcb));
> +	}
> +}
> +

set_memory_decrypted needs to check the return value. I see it
consistently return ENOMEM. I've traced that back to split_large_page
in arch/x86/mm/pat/set_memory.c.