2023-05-15 17:02:18

by Tianyu Lan

Subject: [RFC PATCH V6 08/14] x86/hyperv: Use vmmcall to implement Hyper-V hypercall in sev-snp enlightened guest

From: Tianyu Lan <[email protected]>

In sev-snp enlightened guest, Hyper-V hypercall needs
to use vmmcall to trigger vmexit and notify hypervisor
to handle hypercall request.

Signed-off-by: Tianyu Lan <[email protected]>
---
Change since RFC V2:
* Fix indentation style
---
arch/x86/include/asm/mshyperv.h | 44 ++++++++++++++++++++++++---------
1 file changed, 33 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 97d117ec95c4..939373791249 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -61,16 +61,25 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
u64 hv_status;

#ifdef CONFIG_X86_64
- if (!hv_hypercall_pg)
- return U64_MAX;
+ if (hv_isolation_type_en_snp()) {
+ __asm__ __volatile__("mov %4, %%r8\n"
+ "vmmcall"
+ : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+ "+c" (control), "+d" (input_address)
+ : "r" (output_address)
+ : "cc", "memory", "r8", "r9", "r10", "r11");
+ } else {
+ if (!hv_hypercall_pg)
+ return U64_MAX;

- __asm__ __volatile__("mov %4, %%r8\n"
- CALL_NOSPEC
- : "=a" (hv_status), ASM_CALL_CONSTRAINT,
- "+c" (control), "+d" (input_address)
- : "r" (output_address),
- THUNK_TARGET(hv_hypercall_pg)
- : "cc", "memory", "r8", "r9", "r10", "r11");
+ __asm__ __volatile__("mov %4, %%r8\n"
+ CALL_NOSPEC
+ : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+ "+c" (control), "+d" (input_address)
+ : "r" (output_address),
+ THUNK_TARGET(hv_hypercall_pg)
+ : "cc", "memory", "r8", "r9", "r10", "r11");
+ }
#else
u32 input_address_hi = upper_32_bits(input_address);
u32 input_address_lo = lower_32_bits(input_address);
@@ -104,7 +113,13 @@ static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
u64 hv_status;

#ifdef CONFIG_X86_64
- {
+ if (hv_isolation_type_en_snp()) {
+ __asm__ __volatile__(
+ "vmmcall"
+ : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+ "+c" (control), "+d" (input1)
+ :: "cc", "r8", "r9", "r10", "r11");
+ } else {
__asm__ __volatile__(CALL_NOSPEC
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
"+c" (control), "+d" (input1)
@@ -149,7 +164,14 @@ static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
u64 hv_status;

#ifdef CONFIG_X86_64
- {
+ if (hv_isolation_type_en_snp()) {
+ __asm__ __volatile__("mov %4, %%r8\n"
+ "vmmcall"
+ : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+ "+c" (control), "+d" (input1)
+ : "r" (input2)
+ : "cc", "r8", "r9", "r10", "r11");
+ } else {
__asm__ __volatile__("mov %4, %%r8\n"
CALL_NOSPEC
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
--
2.25.1

2023-05-16 10:44:29

by Peter Zijlstra

Subject: Re: [RFC PATCH V6 08/14] x86/hyperv: Use vmmcall to implement Hyper-V hypercall in sev-snp enlightened guest

On Mon, May 15, 2023 at 12:59:10PM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <[email protected]>
>
> In sev-snp enlightened guest, Hyper-V hypercall needs
> to use vmmcall to trigger vmexit and notify hypervisor
> to handle hypercall request.
>
> Signed-off-by: Tianyu Lan <[email protected]>
> ---
> Change since RFC V2:
> * Fix indentation style
> ---
> arch/x86/include/asm/mshyperv.h | 44 ++++++++++++++++++++++++---------
> 1 file changed, 33 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 97d117ec95c4..939373791249 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -61,16 +61,25 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
> u64 hv_status;
>
> #ifdef CONFIG_X86_64
> - if (!hv_hypercall_pg)
> - return U64_MAX;
> + if (hv_isolation_type_en_snp()) {
> + __asm__ __volatile__("mov %4, %%r8\n"
> + "vmmcall"
> + : "=a" (hv_status), ASM_CALL_CONSTRAINT,
> + "+c" (control), "+d" (input_address)
> + : "r" (output_address)
> + : "cc", "memory", "r8", "r9", "r10", "r11");
> + } else {
> + if (!hv_hypercall_pg)
> + return U64_MAX;
>
> - __asm__ __volatile__("mov %4, %%r8\n"
> - CALL_NOSPEC
> - : "=a" (hv_status), ASM_CALL_CONSTRAINT,
> - "+c" (control), "+d" (input_address)
> - : "r" (output_address),
> - THUNK_TARGET(hv_hypercall_pg)
> - : "cc", "memory", "r8", "r9", "r10", "r11");
> + __asm__ __volatile__("mov %4, %%r8\n"
> + CALL_NOSPEC
> + : "=a" (hv_status), ASM_CALL_CONSTRAINT,
> + "+c" (control), "+d" (input_address)
> + : "r" (output_address),
> + THUNK_TARGET(hv_hypercall_pg)
> + : "cc", "memory", "r8", "r9", "r10", "r11");
> + }

Wouldn't this generate better code with an alternative?