From: Sean Christopherson <seanjc@google.com>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
David Hildenbrand <david@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
"H . Peter Anvin" <hpa@zytor.com>,
Dave Hansen <dave.hansen@intel.com>,
Tony Luck <tony.luck@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Kirill Shutemov <kirill.shutemov@linux.intel.com>,
Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 04/10] x86/tdx: Handle early IO operations
Date: Fri, 5 Nov 2021 21:12:58 +0000 [thread overview]
Message-ID: <YYWeWlmYvotKrX+p@google.com> (raw)
In-Reply-To: <20211005204136.1812078-5-sathyanarayanan.kuppuswamy@linux.intel.com>
On Tue, Oct 05, 2021, Kuppuswamy Sathyanarayanan wrote:
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Reviewed-by: Andi Kleen <ak@linux.intel.com>
Heh, is Andi double-dipping to pad his stats? :-D
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> ---
...
> diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
> index 11e367228e96..4cbffcb737d9 100644
> --- a/arch/x86/kernel/tdx.c
> +++ b/arch/x86/kernel/tdx.c
> @@ -10,6 +10,11 @@
> /* TDX Module call Leaf IDs */
> #define TDGETVEINFO 3
>
> +#define VE_IS_IO_OUT(exit_qual) (((exit_qual) & 8) ? 0 : 1)
> +#define VE_GET_IO_SIZE(exit_qual) (((exit_qual) & 7) + 1)
> +#define VE_GET_PORT_NUM(exit_qual) ((exit_qual) >> 16)
> +#define VE_IS_IO_STRING(exit_qual) ((exit_qual) & 16 ? 1 : 0)
> +
> /*
> * Allocate it in the data region to avoid zeroing it during
> * BSS initialization. It is mainly used in cc_platform_has()
> @@ -228,6 +233,61 @@ int tdx_handle_virtualization_exception(struct pt_regs *regs,
> return ret;
> }
>
> +/*
> + * Handle early IO, mainly for early printks serial output.
> + * This avoids anything that doesn't work early on, like tracing
> + * or printks, by calling the low level functions directly. Any
> + * problems are handled by falling back to a standard early exception.
> + *
> + * Assumes the IO instruction was using ax, which is enforced
> + * by the standard io.h macros.
> + */
> +static __init bool tdx_early_io(struct pt_regs *regs, u32 exit_qual)
> +{
> + struct tdx_hypercall_output outh;
"outh" looks like a typo. Maybe "result" or something alongs those lines?
> + int out, size, port, ret;
> + bool string;
> + u64 mask;
> +
> + string = VE_IS_IO_STRING(exit_qual);
> +
> + /* I/O strings ops are unrolled at build time. */
> + if (string)
Why bother with "string"?
if (VE_IS_IO_STRING(exit_qual))
return false;
> + return 0;
Ugh. This needs to be "return false". "return 0" in the kernel usually means
success, but this horror returns a bool where "false" is failure.
> +
> + out = VE_IS_IO_OUT(exit_qual);
> + size = VE_GET_IO_SIZE(exit_qual);
> + port = VE_GET_PORT_NUM(exit_qual);
> + mask = GENMASK(8 * size, 0);
size * BITS_PER_BYTE
> +
> + ret = _tdx_hypercall(EXIT_REASON_IO_INSTRUCTION, size, out, port,
> + regs->ax, &outh);
This unnecessarily exposes RAX to the untrusted VMM for IN.
> + if (!out && !ret) {
> + regs->ax &= ~mask;
> + regs->ax |= outh.r11 & mask;
> + }
> +
> + return !ret;
> +}
next prev parent reply other threads:[~2021-11-05 21:13 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-05 20:41 [PATCH v7 00/10] Add TDX Guest Support (#VE handler support) Kuppuswamy Sathyanarayanan
2021-10-05 20:41 ` [PATCH v7 01/10] x86/io: Allow to override inX() and outX() implementation Kuppuswamy Sathyanarayanan
2021-10-17 19:27 ` Thomas Gleixner
2021-10-17 20:17 ` Sathyanarayanan Kuppuswamy
2021-10-05 20:41 ` [PATCH v7 02/10] x86/tdx: Add early_is_tdx_guest() interface Kuppuswamy Sathyanarayanan
2021-10-17 19:28 ` Thomas Gleixner
2021-10-05 20:41 ` [PATCH v7 03/10] x86/tdx: Handle port I/O in decompression code Kuppuswamy Sathyanarayanan
2021-10-05 20:41 ` [PATCH v7 04/10] x86/tdx: Handle early IO operations Kuppuswamy Sathyanarayanan
2021-11-05 21:12 ` Sean Christopherson [this message]
2021-11-05 23:08 ` Sathyanarayanan Kuppuswamy
2021-10-05 20:41 ` [PATCH v7 05/10] x86/tdx: Handle port I/O Kuppuswamy Sathyanarayanan
2021-10-17 19:58 ` Thomas Gleixner
2021-10-17 20:35 ` Sathyanarayanan Kuppuswamy
2021-10-18 13:52 ` Tom Lendacky
2021-10-18 18:42 ` Sathyanarayanan Kuppuswamy
2021-11-05 21:23 ` Sean Christopherson
2021-10-05 20:41 ` [PATCH v7 06/10] x86/insn-eval: Introduce insn_get_modrm_reg_ptr() Kuppuswamy Sathyanarayanan
2021-10-05 20:41 ` [PATCH v7 07/10] x86/insn-eval: Introduce insn_decode_mmio() Kuppuswamy Sathyanarayanan
2021-10-05 20:41 ` [PATCH v7 08/10] x86/sev-es: Use insn_decode_mmio() for MMIO implementation Kuppuswamy Sathyanarayanan
2021-10-05 20:41 ` [PATCH v7 09/10] x86/tdx: Handle in-kernel MMIO Kuppuswamy Sathyanarayanan
2021-11-05 22:41 ` Sean Christopherson
2021-10-05 20:41 ` [PATCH v7 10/10] x86/tdx: Handle MWAIT and MONITOR Kuppuswamy Sathyanarayanan
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