From: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Ben Skeggs <bskeggs@redhat.com>,
Karol Herbst <kherbst@redhat.com>, Lyude Paul <lyude@redhat.com>,
xen-devel@lists.xenproject.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, nouveau@lists.freedesktop.org
Subject: Re: [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling
Date: Thu, 18 May 2023 20:18:39 +0200 [thread overview]
Message-ID: <ZGZr/xgbUmVqpOpN@mail-itl> (raw)
In-Reply-To: <20230518134253.909623-3-hch@lst.de>
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On Thu, May 18, 2023 at 03:42:51PM +0200, Christoph Hellwig wrote:
> Remove the dangerous late initialization of xen-swiotlb in
> pci_xen_swiotlb_init_late and instead just always initialize
> xen-swiotlb in the boot code if CONFIG_XEN_PCIDEV_FRONTEND is enabled.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
Doesn't it mean all the PV guests will basically waste 64MB of RAM
by default each if they don't really have PCI devices?
> ---
> arch/x86/include/asm/xen/swiotlb-xen.h | 6 ------
> arch/x86/kernel/pci-dma.c | 25 +++----------------------
> drivers/pci/xen-pcifront.c | 6 ------
> 3 files changed, 3 insertions(+), 34 deletions(-)
>
> diff --git a/arch/x86/include/asm/xen/swiotlb-xen.h b/arch/x86/include/asm/xen/swiotlb-xen.h
> index 77a2d19cc9909e..abde0f44df57dc 100644
> --- a/arch/x86/include/asm/xen/swiotlb-xen.h
> +++ b/arch/x86/include/asm/xen/swiotlb-xen.h
> @@ -2,12 +2,6 @@
> #ifndef _ASM_X86_SWIOTLB_XEN_H
> #define _ASM_X86_SWIOTLB_XEN_H
>
> -#ifdef CONFIG_SWIOTLB_XEN
> -extern int pci_xen_swiotlb_init_late(void);
> -#else
> -static inline int pci_xen_swiotlb_init_late(void) { return -ENXIO; }
> -#endif
> -
> int xen_swiotlb_fixup(void *buf, unsigned long nslabs);
> int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
> unsigned int address_bits,
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index f887b08ac5ffe4..c4a7ead9eb674e 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -81,27 +81,6 @@ static void __init pci_xen_swiotlb_init(void)
> if (IS_ENABLED(CONFIG_PCI))
> pci_request_acs();
> }
> -
> -int pci_xen_swiotlb_init_late(void)
> -{
> - if (dma_ops == &xen_swiotlb_dma_ops)
> - return 0;
> -
> - /* we can work with the default swiotlb */
> - if (!io_tlb_default_mem.nslabs) {
> - int rc = swiotlb_init_late(swiotlb_size_or_default(),
> - GFP_KERNEL, xen_swiotlb_fixup);
> - if (rc < 0)
> - return rc;
> - }
> -
> - /* XXX: this switches the dma ops under live devices! */
> - dma_ops = &xen_swiotlb_dma_ops;
> - if (IS_ENABLED(CONFIG_PCI))
> - pci_request_acs();
> - return 0;
> -}
> -EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
> #else
> static inline void __init pci_xen_swiotlb_init(void)
> {
> @@ -111,7 +90,9 @@ static inline void __init pci_xen_swiotlb_init(void)
> void __init pci_iommu_alloc(void)
> {
> if (xen_pv_domain()) {
> - if (xen_initial_domain() || x86_swiotlb_enable)
> + if (xen_initial_domain() ||
> + IS_ENABLED(CONFIG_XEN_PCIDEV_FRONTEND) ||
> + x86_swiotlb_enable)
> pci_xen_swiotlb_init();
> return;
> }
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index 83c0ab50676dff..11636634ae512f 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -22,7 +22,6 @@
> #include <linux/bitops.h>
> #include <linux/time.h>
> #include <linux/ktime.h>
> -#include <linux/swiotlb.h>
> #include <xen/platform_pci.h>
>
> #include <asm/xen/swiotlb-xen.h>
> @@ -669,11 +668,6 @@ static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
>
> spin_unlock(&pcifront_dev_lock);
>
> - if (!err && !is_swiotlb_active(&pdev->xdev->dev)) {
> - err = pci_xen_swiotlb_init_late();
> - if (err)
> - dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n");
> - }
> return err;
> }
>
> --
> 2.39.2
>
>
--
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
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next prev parent reply other threads:[~2023-05-18 18:18 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 13:42 unexport swiotlb_active Christoph Hellwig
2023-05-18 13:42 ` [PATCH 1/4] x86: move a check out of pci_xen_swiotlb_init Christoph Hellwig
2023-05-18 13:42 ` [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling Christoph Hellwig
2023-05-18 18:18 ` Marek Marczykowski-Górecki [this message]
2023-05-19 4:04 ` Christoph Hellwig
2023-05-19 10:10 ` Marek Marczykowski-Górecki
2023-05-19 12:41 ` Christoph Hellwig
2023-05-19 12:49 ` Andrew Cooper
2023-05-19 12:58 ` Christoph Hellwig
2023-05-20 6:21 ` Christoph Hellwig
2023-05-22 7:52 ` Petr Tesařík
2023-05-22 7:54 ` Petr Tesařík
2023-05-22 8:37 ` Juergen Gross
2023-06-07 13:12 ` Christoph Hellwig
2023-06-09 15:38 ` Juergen Gross
2023-06-12 6:47 ` Christoph Hellwig
2023-06-12 8:08 ` Juergen Gross
2023-06-12 8:23 ` Christoph Hellwig
2023-05-18 13:42 ` [PATCH 3/4] drm/nouveau: stop using is_swiotlb_active Christoph Hellwig
2023-05-18 20:30 ` Lyude Paul
2023-06-07 13:11 ` Christoph Hellwig
2023-05-18 13:42 ` [PATCH 4/4] swiotlb: unexport is_swiotlb_active Christoph Hellwig
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