linux-kernel - Re: [PATCH Part2 RFC v4 15/40] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled

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Message-ID: <YPGnKfDvmgzHCwbI@google.com>
Date:   Fri, 16 Jul 2021 15:35:05 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part2 RFC v4 15/40] crypto: ccp: Handle the legacy TMR
 allocation when SNP is enabled

On Fri, Jul 16, 2021, Brijesh Singh wrote:
> 
> On 7/15/21 6:48 PM, Sean Christopherson wrote:
> > On Wed, Jul 07, 2021, Brijesh Singh wrote:
> >> @@ -1204,16 +1322,6 @@ void sev_pci_init(void)
> >>  	    sev_update_firmware(sev->dev) == 0)
> >>  		sev_get_api_version();
> >>  
> >> -	/* Obtain the TMR memory area for SEV-ES use */
> >> -	tmr_page = alloc_pages(GFP_KERNEL, get_order(SEV_ES_TMR_SIZE));
> >> -	if (tmr_page) {
> >> -		sev_es_tmr = page_address(tmr_page);
> >> -	} else {
> >> -		sev_es_tmr = NULL;
> >> -		dev_warn(sev->dev,
> >> -			 "SEV: TMR allocation failed, SEV-ES support unavailable\n");
> >> -	}
> >> -
> >>  	/*
> >>  	 * If boot CPU supports the SNP, then first attempt to initialize
> >>  	 * the SNP firmware.
> >> @@ -1229,6 +1337,16 @@ void sev_pci_init(void)
> >>  		}
> >>  	}
> >>  
> >> +	/* Obtain the TMR memory area for SEV-ES use */
> >> +	tmr_page = __snp_alloc_firmware_pages(GFP_KERNEL, get_order(sev_es_tmr_size), false);
> >> +	if (tmr_page) {
> >> +		sev_es_tmr = page_address(tmr_page);
> >> +	} else {
> >> +		sev_es_tmr = NULL;
> >> +		dev_warn(sev->dev,
> >> +			 "SEV: TMR allocation failed, SEV-ES support unavailable\n");
> >> +	}
> > I think your patch ordering got a bit wonky.  AFAICT, the chunk that added
> > sev_snp_init() and friends in the previous patch 14 should have landed above
> > the TMR allocation, i.e. the code movement here should be unnecessary.
> 
> I was debating about it whether to include all the SNP supports in one
> patch or divide it up. If I had included all legacy support new
> requirement in the same patch which adds the SNP then it will be a big
> patch. I had feeling that others may ask me to split it.

It wasn't comment on the patch organization, rather that the code added in patch 14
appears to have landed in the wrong location within the code.  The above diff shows
that the TMR allocation is being moved around the SNP initialization code that was
added in patch 14 (the immediately prior patch).  Presumably the required order
doesn't magically change just because the TMR is now being allocated as a 2mb blob,
so either the code movement is unnecessary churn or the original location was wrong.
In either case, landing the SNP initialization code above the TMR allocation in
patch 14 would eliminate the above code movement.