linux-kernel - RE: [PATCH RESEND v9 2/2] x86/tdx: Support vmalloc() for tdx_enc_status

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Date:   Fri, 11 Aug 2023 19:08:10 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
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        "dan.j.williams@...el.com" <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>,
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        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
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        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
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        Anthony Davis <andavis@...hat.com>,
        Mark Heslin <mheslin@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "xiaoyao.li@...el.com" <xiaoyao.li@...el.com>
Subject: RE: [PATCH RESEND v9 2/2] x86/tdx: Support vmalloc() for
 tdx_enc_status_changed()

> From: Dave Hansen <dave.hansen@...el.com>
> Sent: Friday, August 11, 2023 7:10 AM
> [...]
> This creates two different paths for vmalloc() and the direct map.
> There are two different ways to do va=>pa conversion, for instance.
> Here's a single loop that works for both cases:
> 
> 	unsigned long step = end - start;
> 	unsigned long addr;
> 
> 	/* Step through page-by-page for vmalloc() mappings: */
> 	if (is_vmalloc_addr((void *)vaddr))
> 		step = PAGE_SIZE;
> 
> 	for (addr = start; addr < end; addr += step) {
> 		phys_addr_t start_pa = slow_virt_to_phys(addr);
> 		phys_addr_t end_pa   = start_pa + step;
> 
> 		if (!tdx_enc_status_changed_phys(start_pa, end_pa, enc))
> 			return false;
> 	}
> 
> Note that this also doesn't abuse 'start' by making it a loop variable.
> It also, uh, uses a for() loop.
> 
> The only downside is that it costs a page table walk for direct map
> virt=>phys conversion.  I can live with that.

Your version is concise and more readable.  
Thanks for improving the patch! I'll use this in v10 shortly.