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Date: Wed, 28 Jun 2023 15:23:42 +0300
From: kirill.shutemov@...ux.intel.com
To: Kai Huang <kai.huang@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
linux-mm@...ck.org, x86@...nel.org, dave.hansen@...el.com,
tony.luck@...el.com, peterz@...radead.org, tglx@...utronix.de,
bp@...en8.de, mingo@...hat.com, hpa@...or.com, seanjc@...gle.com,
pbonzini@...hat.com, david@...hat.com, dan.j.williams@...el.com,
rafael.j.wysocki@...el.com, ashok.raj@...el.com,
reinette.chatre@...el.com, len.brown@...el.com, ak@...ux.intel.com,
isaku.yamahata@...el.com, ying.huang@...el.com, chao.gao@...el.com,
sathyanarayanan.kuppuswamy@...ux.intel.com, nik.borisov@...e.com,
bagasdotme@...il.com, sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v12 18/22] x86/virt/tdx: Keep TDMRs when module
initialization is successful
On Tue, Jun 27, 2023 at 02:12:48AM +1200, Kai Huang wrote:
> On the platforms with the "partial write machine check" erratum, the
> kexec() needs to convert all TDX private pages back to normal before
> booting to the new kernel. Otherwise, the new kernel may get unexpected
> machine check.
>
> There's no existing infrastructure to track TDX private pages. Change
> to keep TDMRs when module initialization is successful so that they can
> be used to find PAMTs.
>
> With this change, only put_online_mems() and freeing the buffer of the
> TDSYSINFO_STRUCT and CMR array still need to be done even when module
> initialization is successful. Adjust the error handling to explicitly
> do them when module initialization is successful and unconditionally
> clean up the rest when initialization fails.
>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>
> v11 -> v12 (new patch):
> - Defer keeping TDMRs logic to this patch for better review
> - Improved error handling logic (Nikolay/Kirill in patch 15)
>
> ---
> arch/x86/virt/vmx/tdx/tdx.c | 84 ++++++++++++++++++-------------------
> 1 file changed, 42 insertions(+), 42 deletions(-)
>
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 52b7267ea226..85b24b2e9417 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -49,6 +49,8 @@ static DEFINE_MUTEX(tdx_module_lock);
> /* All TDX-usable memory regions. Protected by mem_hotplug_lock. */
> static LIST_HEAD(tdx_memlist);
>
> +static struct tdmr_info_list tdx_tdmr_list;
> +
> /*
> * Wrapper of __seamcall() to convert SEAMCALL leaf function error code
> * to kernel error code. @seamcall_ret and @out contain the SEAMCALL
> @@ -1047,7 +1049,6 @@ static int init_tdmrs(struct tdmr_info_list *tdmr_list)
> static int init_tdx_module(void)
> {
> struct tdsysinfo_struct *sysinfo;
> - struct tdmr_info_list tdmr_list;
> struct cmr_info *cmr_array;
> int ret;
>
> @@ -1088,17 +1089,17 @@ static int init_tdx_module(void)
> goto out_put_tdxmem;
>
> /* Allocate enough space for constructing TDMRs */
> - ret = alloc_tdmr_list(&tdmr_list, sysinfo);
> + ret = alloc_tdmr_list(&tdx_tdmr_list, sysinfo);
> if (ret)
> goto out_free_tdxmem;
>
> /* Cover all TDX-usable memory regions in TDMRs */
> - ret = construct_tdmrs(&tdx_memlist, &tdmr_list, sysinfo);
> + ret = construct_tdmrs(&tdx_memlist, &tdx_tdmr_list, sysinfo);
> if (ret)
> goto out_free_tdmrs;
>
> /* Pass the TDMRs and the global KeyID to the TDX module */
> - ret = config_tdx_module(&tdmr_list, tdx_global_keyid);
> + ret = config_tdx_module(&tdx_tdmr_list, tdx_global_keyid);
> if (ret)
> goto out_free_pamts;
>
> @@ -1118,51 +1119,50 @@ static int init_tdx_module(void)
> goto out_reset_pamts;
>
> /* Initialize TDMRs to complete the TDX module initialization */
> - ret = init_tdmrs(&tdmr_list);
> + ret = init_tdmrs(&tdx_tdmr_list);
> + if (ret)
> + goto out_reset_pamts;
> +
> + pr_info("%lu KBs allocated for PAMT.\n",
> + tdmrs_count_pamt_kb(&tdx_tdmr_list));
> +
> + /*
> + * @tdx_memlist is written here and read at memory hotplug time.
> + * Lock out memory hotplug code while building it.
> + */
> + put_online_mems();
> + /*
> + * For now both @sysinfo and @cmr_array are only used during
> + * module initialization, so always free them.
> + */
> + free_page((unsigned long)sysinfo);
> +
> + return 0;
> out_reset_pamts:
> - if (ret) {
> - /*
> - * Part of PAMTs may already have been initialized by the
> - * TDX module. Flush cache before returning PAMTs back
> - * to the kernel.
> - */
> - wbinvd_on_all_cpus();
> - /*
> - * According to the TDX hardware spec, if the platform
> - * doesn't have the "partial write machine check"
> - * erratum, any kernel read/write will never cause #MC
> - * in kernel space, thus it's OK to not convert PAMTs
> - * back to normal. But do the conversion anyway here
> - * as suggested by the TDX spec.
> - */
> - tdmrs_reset_pamt_all(&tdmr_list);
> - }
> + /*
> + * Part of PAMTs may already have been initialized by the
> + * TDX module. Flush cache before returning PAMTs back
> + * to the kernel.
> + */
> + wbinvd_on_all_cpus();
> + /*
> + * According to the TDX hardware spec, if the platform
> + * doesn't have the "partial write machine check"
> + * erratum, any kernel read/write will never cause #MC
> + * in kernel space, thus it's OK to not convert PAMTs
> + * back to normal. But do the conversion anyway here
> + * as suggested by the TDX spec.
> + */
> + tdmrs_reset_pamt_all(&tdx_tdmr_list);
> out_free_pamts:
> - if (ret)
> - tdmrs_free_pamt_all(&tdmr_list);
> - else
> - pr_info("%lu KBs allocated for PAMT.\n",
> - tdmrs_count_pamt_kb(&tdmr_list));
> + tdmrs_free_pamt_all(&tdx_tdmr_list);
> out_free_tdmrs:
> - /*
> - * Always free the buffer of TDMRs as they are only used during
> - * module initialization.
> - */
> - free_tdmr_list(&tdmr_list);
> + free_tdmr_list(&tdx_tdmr_list);
> out_free_tdxmem:
> - if (ret)
> - free_tdx_memlist(&tdx_memlist);
> + free_tdx_memlist(&tdx_memlist);
> out_put_tdxmem:
> - /*
> - * @tdx_memlist is written here and read at memory hotplug time.
> - * Lock out memory hotplug code while building it.
> - */
> put_online_mems();
> out:
> - /*
> - * For now both @sysinfo and @cmr_array are only used during
> - * module initialization, so always free them.
> - */
> free_page((unsigned long)sysinfo);
> return ret;
> }
This diff is extremely hard to follow, but I think the change to error
handling Nikolay proposed has to be applied to the function from the
beginning, not changed drastically in this patch.
--
Kiryl Shutsemau / Kirill A. Shutemov
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