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Message-ID: <BYAPR21MB1688A412FCBEBB3189107102D7139@BYAPR21MB1688.namprd21.prod.outlook.com>
Date: Mon, 28 Nov 2022 01:20:42 +0000
From: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To: Dexuan Cui <decui@...rosoft.com>,
"ak@...ux.intel.com" <ak@...ux.intel.com>,
"arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
"brijesh.singh@....com" <brijesh.singh@....com>,
"Williams, Dan J" <dan.j.williams@...el.com>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
"hpa@...or.com" <hpa@...or.com>,
"jane.chu@...cle.com" <jane.chu@...cle.com>,
"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
KY Srinivasan <kys@...rosoft.com>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"luto@...nel.org" <luto@...nel.org>,
"mingo@...hat.com" <mingo@...hat.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"sathyanarayanan.kuppuswamy@...ux.intel.com"
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
"seanjc@...gle.com" <seanjc@...gle.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"tony.luck@...el.com" <tony.luck@...el.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
"x86@...nel.org" <x86@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 5/6] x86/hyperv: Support hypercalls for TDX guests
From: Dexuan Cui <decui@...rosoft.com> Sent: Sunday, November 27, 2022 4:59 PM
>
> > From: Michael Kelley (LINUX) <mikelley@...rosoft.com>
> > Sent: Wednesday, November 23, 2022 6:45 AM
> > To: Dexuan Cui <decui@...rosoft.com>; ak@...ux.intel.com; arnd@...db.de;
> >
> > Two thoughts:
> >
> > 1) The #ifdef CONFIG_INTEL_TDX_GUEST could probably be removed entirely
> > with a tweak. hv_isolation_type_tdx() already doesn't need the #ifdef asthere's
> > already a stub that returns 'false'. Then you just need a way to handle
> > __tdx_ms_hv_hypercall(), or whatever it becomes based on the other discussion.
> > As long as you can provide a stub that does nothing, the #ifdef won't be needed.
> >
> > 2) Assuming that we end up with some kind of Hyper-V specific version of
> > __tdx_hypercall(), and hopefully as a "C" function, could you move the handling
> > of ms_hyperv.shared_gpa_boundary into that function? Then you won't need
> > to break out a separate include file for struct ms_hyperv. The Hyper-V TDX
> > hypercall function must handle both normal and "fast" hypercalls, and the
> > shared_gpa_boundary adjustment is needed only for normal hypercalls,
> > but you can check the "fast" bit in the control word to decide.
> >
> > I haven't coded these ideas, so maybe there are snags I haven't thought of.
> > But I'm really hoping we can avoid having to create a separate include
> > file for struct ms_hyperv.
> >
> > Michael
>
> Thanks for the great suggestions! Now the code looks like this:
> (the full list of v2 patches are still WIP:
>
> https://github.com/dcui/tdx/commits/decui/hyperv-next/2022-1121/v6.1-rc5/v2
>
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index 13ccb52eecd7..00e5c84e380b 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -276,6 +276,27 @@ bool hv_isolation_type_tdx(void)
> {
> return static_branch_unlikely(&isolation_type_tdx);
> }
> +
> +u64 hv_tdx_hypercall(u64 control, u64 input_addr, u64 output_addr)
> +{
> + struct tdx_hypercall_args args = { };
> +
> + if (!(control & HV_HYPERCALL_FAST_BIT)) {
> + if (input_addr)
> + input_addr += ms_hyperv.shared_gpa_boundary;
At one point when working with the vTOM code, I realized that or'ing in
the shared_gpa_boundary is probably safer than add'ing it, just in case
the physical address already has vTOM set. I don't know if that possibility
exists here, but it's something to consider as being slightly more robust.
> +
> + if (output_addr)
> + output_addr += ms_hyperv.shared_gpa_boundary;
Same here.
> + }
> +
> + args.r10 = control;
> + args.rdx = input_addr;
> + args.r8 = output_addr;
> +
> + (void)__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT);
> +
> + return args.r11;
> +}
> #endif
>
> /*
>
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 8a2cafec4675..1be7bcf0d7d1 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -39,6 +39,8 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32
> num_pages);
> int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
> int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
>
> +u64 hv_tdx_hypercall(u64 control, u64 input_addr, u64 output_addr);
> +
> static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
> {
> u64 input_address = input ? virt_to_phys(input) : 0;
> @@ -46,6 +48,9 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void
> *output)
> u64 hv_status;
>
> #ifdef CONFIG_X86_64
> + if (hv_isolation_type_tdx())
> + return hv_tdx_hypercall(control, input_address, output_address);
> +
> if (!hv_hypercall_pg)
> return U64_MAX;
>
> @@ -83,6 +88,9 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
> u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
>
> #ifdef CONFIG_X86_64
> + if (hv_isolation_type_tdx())
> + return hv_tdx_hypercall(control, input1, 0);
> +
> {
> __asm__ __volatile__(CALL_NOSPEC
> : "=a" (hv_status), ASM_CALL_CONSTRAINT,
> @@ -114,6 +122,9 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1,
> u64 input2)
> u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
>
> #ifdef CONFIG_X86_64
> + if (hv_isolation_type_tdx())
> + return hv_tdx_hypercall(control, input1, input2);
> +
> {
> __asm__ __volatile__("mov %4, %%r8\n"
> CALL_NOSPEC
Yes. This new structure LGTM.
Michael
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