linux-kernel - Re: [PATCH v3 06/21] x86/virt/tdx: Shut down TDX module in case of error

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Message-ID: <b3c81b7f-3016-8f4e-3ac5-bff1fc52a879@intel.com>
Date:   Tue, 26 Apr 2022 13:59:37 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, pbonzini@...hat.com, len.brown@...el.com,
        tony.luck@...el.com, rafael.j.wysocki@...el.com,
        reinette.chatre@...el.com, dan.j.williams@...el.com,
        peterz@...radead.org, ak@...ux.intel.com,
        kirill.shutemov@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        isaku.yamahata@...el.com
Subject: Re: [PATCH v3 06/21] x86/virt/tdx: Shut down TDX module in case of
 error

On 4/5/22 21:49, Kai Huang wrote:
> TDX supports shutting down the TDX module at any time during its
> lifetime.  After TDX module is shut down, no further SEAMCALL can be
> made on any logical cpu.

Is this strictly true?

I thought SEAMCALLs were used for the P-SEAMLDR too.

> Shut down the TDX module in case of any error happened during the
> initialization process.  It's pointless to leave the TDX module in some
> middle state.
> 
> Shutting down the TDX module requires calling TDH.SYS.LP.SHUTDOWN on all
> BIOS-enabled cpus, and the SEMACALL can run concurrently on different
> cpus.  Implement a mechanism to run SEAMCALL concurrently on all online
> cpus.  Logical-cpu scope initialization will use it too.
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>  arch/x86/virt/vmx/tdx/tdx.c | 40 ++++++++++++++++++++++++++++++++++++-
>  arch/x86/virt/vmx/tdx/tdx.h |  5 +++++
>  2 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 674867bccc14..faf8355965a5 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -11,6 +11,8 @@
>  #include <linux/cpumask.h>
>  #include <linux/mutex.h>
>  #include <linux/cpu.h>
> +#include <linux/smp.h>
> +#include <linux/atomic.h>
>  #include <asm/msr-index.h>
>  #include <asm/msr.h>
>  #include <asm/cpufeature.h>
> @@ -328,6 +330,39 @@ static int seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
>  	return 0;
>  }
>  
> +/* Data structure to make SEAMCALL on multiple CPUs concurrently */
> +struct seamcall_ctx {
> +	u64 fn;
> +	u64 rcx;
> +	u64 rdx;
> +	u64 r8;
> +	u64 r9;
> +	atomic_t err;
> +	u64 seamcall_ret;
> +	struct tdx_module_output out;
> +};
> +
> +static void seamcall_smp_call_function(void *data)
> +{
> +	struct seamcall_ctx *sc = data;
> +	int ret;
> +
> +	ret = seamcall(sc->fn, sc->rcx, sc->rdx, sc->r8, sc->r9,
> +			&sc->seamcall_ret, &sc->out);
> +	if (ret)
> +		atomic_set(&sc->err, ret);
> +}
> +
> +/*
> + * Call the SEAMCALL on all online cpus concurrently.
> + * Return error if SEAMCALL fails on any cpu.
> + */
> +static int seamcall_on_each_cpu(struct seamcall_ctx *sc)
> +{
> +	on_each_cpu(seamcall_smp_call_function, sc, true);
> +	return atomic_read(&sc->err);
> +}

Why bother returning something that's not read?

>  static inline bool p_seamldr_ready(void)
>  {
>  	return !!p_seamldr_info.p_seamldr_ready;
> @@ -437,7 +472,10 @@ static int init_tdx_module(void)
>  
>  static void shutdown_tdx_module(void)
>  {
> -	/* TODO: Shut down the TDX module */
> +	struct seamcall_ctx sc = { .fn = TDH_SYS_LP_SHUTDOWN };
> +
> +	seamcall_on_each_cpu(&sc);
> +
>  	tdx_module_status = TDX_MODULE_SHUTDOWN;
>  }
>  
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 6990c93198b3..dcc1f6dfe378 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -35,6 +35,11 @@ struct p_seamldr_info {
>  #define P_SEAMLDR_SEAMCALL_BASE		BIT_ULL(63)
>  #define P_SEAMCALL_SEAMLDR_INFO		(P_SEAMLDR_SEAMCALL_BASE | 0x0)
>  
> +/*
> + * TDX module SEAMCALL leaf functions
> + */
> +#define TDH_SYS_LP_SHUTDOWN	44
> +
>  struct tdx_module_output;
>  u64 __seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
>  	       struct tdx_module_output *out);