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Message-ID: <SA1PR21MB1335A32E8CAB43057538DB57BF139@SA1PR21MB1335.namprd21.prod.outlook.com>
Date: Mon, 28 Nov 2022 21:53:35 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: Dave Hansen <dave.hansen@...el.com>,
"Michael Kelley (LINUX)" <mikelley@...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: Dave Hansen <dave.hansen@...el.com>
> Sent: Monday, November 28, 2022 1:15 PM
> [...]
> This is the point where the maintainer gets a wee bit grumpy. The page
> I just pointed you to (twice) has this nice quote:
>
> If the hypercall involves no input or output parameters, the
> hypervisor ignores the corresponding GPA pointer.
>
> So, bravo to your colleagues who nicely documented this. But,
> unfortunately, you didn't take advantage of their great documentation.
> Instead, you made me search for it to provide actual facts to combat the
> weak conjecture you offered above.
Sorry, I should really have read the document before starting to conjecture...
> > The above is just my conjecture. I don't know how exactly Hyper-V works.
>
> I do! I literally Googled "HV HYPERCALL FAST BIT" and the first page
> that came up told me all I needed to know.
>
> I could be merrily merging your patches. But, instead, I'm reading
> documentation that can be trivially found and repeatedly regurgitating it.
>
> Please, slow down. Take some time to answer emails and do it more
> deliberately. This isn't a race.
Thanks, I learn a lesson. Hopefully the below looks good enough.
Compared to the earlier version, the only changes are: 1) simplified the
change in hv_do_hypercall(); 2) added a comment before the function.
BTW, I can't post the v2 patchset right now, as I'm waiting for Kirill to
expand __tdx_hypercall() first:
https://lwn.net/ml/linux-kernel/SA1PR21MB1335EEEC1DE4CB42F6477A5EBF0C9@SA1PR21MB1335.namprd21.prod.outlook.com/
I'm also thinking about how to properly address the vmalloc
issue with tdx_enc_status_changed().
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 70170049be2c..41395891d112 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -242,6 +242,20 @@ bool hv_isolation_type_tdx(void)
{
return static_branch_unlikely(&isolation_type_tdx);
}
+
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
+{
+ struct tdx_hypercall_args args = { };
+
+ args.r10 = control;
+ args.rdx = param1;
+ args.r8 = param2;
+
+ (void)__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT);
+
+ return args.r11;
+}
+EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
#endif
/*
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 9cc6db45c3bc..055b6fb8941f 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -10,6 +10,7 @@
#include <asm/nospec-branch.h>
#include <asm/paravirt.h>
#include <asm/mshyperv.h>
+#include <asm/coco.h>
union hv_ghcb;
@@ -39,6 +40,12 @@ 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 param1, u64 param2);
+
+/*
+ * If the hypercall involves no input or output parameters, the hypervisor
+ * ignores the corresponding GPA pointer.
+ */
static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
{
u64 input_address = input ? virt_to_phys(input) : 0;
@@ -46,6 +53,10 @@ 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,
+ cc_mkdec(input_address),
+ cc_mkdec(output_address));
if (!hv_hypercall_pg)
return U64_MAX;
@@ -83,6 +94,9 @@ 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 +128,9 @@ 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
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