linux-kernel - RE: [PATCH 06/15] hyperv: avoid unnecessary vmalloc

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Message-ID: <DM5PR03MB249020520F8A94171FA9BA99A0930@DM5PR03MB2490.namprd03.prod.outlook.com>
Date:   Wed, 21 Dec 2016 19:19:39 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Roman Kagan <rkagan@...tuozzo.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "Haiyang Zhang" <haiyangz@...rosoft.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "Denis V . Lunev" <den@...nvz.org>
Subject: RE: [PATCH 06/15] hyperv: avoid unnecessary vmalloc



> -----Original Message-----
> From: Roman Kagan [mailto:rkagan@...tuozzo.com]
> Sent: Tuesday, December 20, 2016 7:56 AM
> To: Paolo Bonzini <pbonzini@...hat.com>; Radim Krčmář
> <rkrcmar@...hat.com>; KY Srinivasan <kys@...rosoft.com>; Vitaly
> Kuznetsov <vkuznets@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>; Ingo Molnar
> <mingo@...hat.com>; H. Peter Anvin <hpa@...or.com>; x86@...nel.org;
> Haiyang Zhang <haiyangz@...rosoft.com>; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; devel@...uxdriverproject.org; Denis V . Lunev
> <den@...nvz.org>; Roman Kagan <rkagan@...tuozzo.com>
> Subject: [PATCH 06/15] hyperv: avoid unnecessary vmalloc
> 
> Make hypercall and tsc page allocation similar to the rest of the
> Hyper-V shared memory stuff instead of vmalloc-ing them.
> 
> Also perform cleanup unconditionally which is safe.
> 
> TODO: the skipping of free in case of a crash is probably no longer
> necessary, too.

Please breakup these patches.
> 
> Signed-off-by: Roman Kagan <rkagan@...tuozzo.com>
> ---
>  drivers/hv/hv.c | 42 ++++++++++++++++++------------------------
>  1 file changed, 18 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 6bbc0b09..b40c7d9 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -29,6 +29,7 @@
>  #include <linux/version.h>
>  #include <linux/interrupt.h>
>  #include <linux/clockchips.h>
> +#include <asm/cacheflush.h>
>  #include <asm/hyperv.h>
>  #include <asm/mshyperv.h>
>  #include "hyperv_vmbus.h"
> @@ -208,14 +209,15 @@ int hv_init(void)
>  	/* See if the hypercall page is already set */
>  	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> 
> -	virtaddr = __vmalloc(PAGE_SIZE, GFP_KERNEL,
> PAGE_KERNEL_EXEC);
> -
> -	if (!virtaddr)
> +	virtaddr = (void *)get_zeroed_page(GFP_KERNEL);
> +	if (!virtaddr || set_memory_x((unsigned long)virtaddr, 1))
>  		goto cleanup;

Have you tested this patch.
> +	hv_context.hypercall_page = virtaddr;
> 
>  	hypercall_msr.enable = 1;
> 
> -	hypercall_msr.guest_physical_address = vmalloc_to_pfn(virtaddr);
> +	hypercall_msr.guest_physical_address =
> +				virt_to_phys(virtaddr) >> PAGE_SHIFT;
>  	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> 
>  	/* Confirm that hypercall page did get setup. */
> @@ -225,14 +227,12 @@ int hv_init(void)
>  	if (!hypercall_msr.enable)
>  		goto cleanup;
> 
> -	hv_context.hypercall_page = virtaddr;
> -
>  #ifdef CONFIG_X86_64
>  	if (ms_hyperv.features &
> HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
>  		union hv_x64_msr_hypercall_contents tsc_msr;
>  		void *va_tsc;
> 
> -		va_tsc = __vmalloc(PAGE_SIZE, GFP_KERNEL,
> PAGE_KERNEL);
> +		va_tsc = (void *)get_zeroed_page(GFP_KERNEL);
>  		if (!va_tsc)
>  			goto cleanup;
>  		hv_context.tsc_page = va_tsc;
> @@ -240,7 +240,8 @@ int hv_init(void)
>  		rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
> 
>  		tsc_msr.enable = 1;
> -		tsc_msr.guest_physical_address = vmalloc_to_pfn(va_tsc);
> +		tsc_msr.guest_physical_address =
> +				virt_to_phys(va_tsc) >> PAGE_SHIFT;
> 
>  		wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
>  		clocksource_register_hz(&hyperv_cs_tsc,
> NSEC_PER_SEC/100);
> @@ -249,14 +250,9 @@ int hv_init(void)
>  	return 0;
> 
>  cleanup:
> -	if (virtaddr) {
> -		if (hypercall_msr.enable) {
> -			hypercall_msr.as_uint64 = 0;
> -			wrmsrl(HV_X64_MSR_HYPERCALL,
> hypercall_msr.as_uint64);
> -		}
> -
> -		vfree(virtaddr);
> -	}
> +	hypercall_msr.as_uint64 = 0;
> +	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +	free_page((unsigned long)virtaddr);
> 
>  	return -ENOTSUPP;
>  }
> @@ -273,13 +269,11 @@ void hv_cleanup(bool crash)
>  	/* Reset our OS id */
>  	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
> 
> -	if (hv_context.hypercall_page) {
> -		hypercall_msr.as_uint64 = 0;
> -		wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> -		if (!crash)
> -			vfree(hv_context.hypercall_page);
> -		hv_context.hypercall_page = NULL;
> -	}
> +	hypercall_msr.as_uint64 = 0;
> +	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +	if (!crash)
> +		free_page((unsigned long)hv_context.hypercall_page);
> +	hv_context.hypercall_page = NULL;
> 
>  #ifdef CONFIG_X86_64
>  	/*
> @@ -298,7 +292,7 @@ void hv_cleanup(bool crash)
>  		hypercall_msr.as_uint64 = 0;
>  		wrmsrl(HV_X64_MSR_REFERENCE_TSC,
> hypercall_msr.as_uint64);
>  		if (!crash)
> -			vfree(hv_context.tsc_page);
> +			free_page((unsigned long)hv_context.tsc_page);
>  		hv_context.tsc_page = NULL;
>  	}
>  #endif
> --
> 2.9.3