Re: [PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image

Borislav Petkov
2020-05-20T09:14:27Z

On Tue, Apr 28, 2020 at 05:16:50PM +0200, Joerg Roedel wrote:
> +static inline u64 sev_es_rd_ghcb_msr(void)
> +{
> + return native_read_msr(MSR_AMD64_SEV_ES_GHCB);
> +}
> +
> +static inline void sev_es_wr_ghcb_msr(u64 val)
> +{
> + u32 low, high;
> +
> + low = (u32)(val);
> + high = (u32)(val >> 32);
> +
> + native_write_msr(MSR_AMD64_SEV_ES_GHCB, low, high);
> +}

Instead of duplicating those two, you can lift the ones in the
compressed image into sev-es.h and use them here. I don't care one bit
about the MSR tracepoints in native_*_msr().

> +static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
> + char *dst, char *buf, size_t size)
> +{
> + unsigned long error_code = X86_PF_PROT | X86_PF_WRITE;
> + char __user *target = (char __user *)dst;
> + u64 d8;
> + u32 d4;
> + u16 d2;
> + u8 d1;
> +
> + switch (size) {
> + case 1:
> + memcpy(&d1, buf, 1);
> + if (put_user(d1, target))
> + goto fault;
> + break;
> + case 2:
> + memcpy(&d2, buf, 2);
> + if (put_user(d2, target))
> + goto fault;
> + break;
> + case 4:
> + memcpy(&d4, buf, 4);
> + if (put_user(d4, target))
> + goto fault;
> + break;
> + case 8:
> + memcpy(&d8, buf, 8);
> + if (put_user(d8, target))
> + goto fault;

Ok, those (and below) memcpys get nicely optimized to MOVs by the
compiler here.

--
Regards/Gruss,
Boris.