[{"id":3687211,"web_url":"http://patchwork.ozlabs.org/comment/3687211/","msgid":"<20260506155418.GA790442@bhelgaas>","list_archive_url":null,"date":"2026-05-06T15:54:18","subject":"Re: [PATCH v6 1/6] PCI/TPH: Fix pcie_tph_get_st_table_loc() field\n extraction","submitter":{"id":67298,"url":"http://patchwork.ozlabs.org/api/people/67298/","name":"Bjorn Helgaas","email":"helgaas@kernel.org"},"content":"On Wed, May 06, 2026 at 05:46:18PM +0800, Chengwen Feng wrote:\n> pcie_tph_get_st_table_loc() incorrectly uses FIELD_GET(), which shifts the\n> field value to bit 0. But the function is designed to return raw\n> PCI_TPH_LOC_* values as defined in the function comment.\n> \n> This causes incorrect ST table location detection. Fix it by using bitwise\n> AND with PCI_TPH_CAP_LOC_MASK to return the unshifted field value matching\n> the function specification.\n> \n> While this change appears to be a no-op within tph.c, the external caller\n> mlx5_st_create() relies on the documented function behavior, making this\n> fix necessary.\n\nPreviously, pcie_tph_get_st_table_loc() returned 0x0 (for\nPCI_TPH_LOC_NONE), 0x2 (for PCI_TPH_LOC_CAP), or 0x4 (for\nPCI_TPH_LOC_MSIX).\n\nmlx5_st_create() is currently the only external caller. It only\nchecks for PCI_TPH_LOC_NONE, which is 0 regardless of the FIELD_GET(),\nso I don't think this actually fixes mlx5_st_create().\n\nProbably still worth a stable backport because other drivers may call\npcie_tph_get_st_table_loc() in the future, and if they depend on\nPCI_TPH_LOC_CAP or PCI_TPH_LOC_MSIX, and are backported to stable\nkernels, they will need this.\n\nI might reword that last paragraph to avoid the implication that this\nactually fixes something in mlx5:\n\n This doesn't make a difference to mlx5_st_create(), the lone\n external caller, because it only checks for PCI_TPH_LOC_NONE (0),\n but will be needed for callers that check for PCI_TPH_LOC_CAP or\n PCI_TPH_LOC_MSIX.\n\n> Fixes: d2e8a34876ce (\"PCI/TPH: Add Steering Tag support\")\n> Cc: stable@vger.kernel.org\n> Signed-off-by: Chengwen Feng \n> Reviewed-by: Alex Williamson \n\nReviewed-by: Bjorn Helgaas \n\nFeel free to merge along with the rest, I assume via the VFIO tree.\n\n> ---\n> drivers/pci/tph.c | 8 +-------\n> 1 file changed, 1 insertion(+), 7 deletions(-)\n> \n> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c\n> index 91145e8d9d95..f17b74b5fb1e 100644\n> --- a/drivers/pci/tph.c\n> +++ b/drivers/pci/tph.c\n> @@ -170,7 +170,7 @@ u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev)\n> \n> \tpci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, ®);\n> \n> -\treturn FIELD_GET(PCI_TPH_CAP_LOC_MASK, reg);\n> +\treturn reg & PCI_TPH_CAP_LOC_MASK;\n> }\n> EXPORT_SYMBOL(pcie_tph_get_st_table_loc);\n> \n> @@ -183,11 +183,7 @@ u16 pcie_tph_get_st_table_size(struct pci_dev *pdev)\n> \tu32 reg;\n> \tu32 loc;\n> \n> -\t/* Check ST table location first */\n> \tloc = pcie_tph_get_st_table_loc(pdev);\n> -\n> -\t/* Convert loc to match with PCI_TPH_LOC_* defined in pci_regs.h */\n> -\tloc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);\n> \tif (loc != PCI_TPH_LOC_CAP)\n> \t\treturn 0;\n> \n> @@ -316,8 +312,6 @@ int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index, u16 tag)\n> \tset_ctrl_reg_req_en(pdev, PCI_TPH_REQ_DISABLE);\n> \n> \tloc = pcie_tph_get_st_table_loc(pdev);\n> -\t/* Convert loc to match with PCI_TPH_LOC_* */\n> -\tloc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);\n> \n> \tswitch (loc) {\n> \tcase PCI_TPH_LOC_MSIX:\n> -- \n> 2.17.1\n>","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=dvWE085q;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.105.105.114; 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charset=us-ascii","Content-Disposition":"inline","In-Reply-To":"<20260506094623.29327-2-fengchengwen@huawei.com>"}},{"id":3690626,"web_url":"http://patchwork.ozlabs.org/comment/3690626/","msgid":"<20260513070101.GD15586@unreal>","list_archive_url":null,"date":"2026-05-13T07:01:01","subject":"Re: [PATCH v6 1/6] PCI/TPH: Fix pcie_tph_get_st_table_loc() field\n extraction","submitter":{"id":68852,"url":"http://patchwork.ozlabs.org/api/people/68852/","name":"Leon Romanovsky","email":"leon@kernel.org"},"content":"On Wed, May 06, 2026 at 10:54:18AM -0500, Bjorn Helgaas wrote:\n> On Wed, May 06, 2026 at 05:46:18PM +0800, Chengwen Feng wrote:\n> > pcie_tph_get_st_table_loc() incorrectly uses FIELD_GET(), which shifts the\n> > field value to bit 0. But the function is designed to return raw\n> > PCI_TPH_LOC_* values as defined in the function comment.\n> > \n> > This causes incorrect ST table location detection. Fix it by using bitwise\n> > AND with PCI_TPH_CAP_LOC_MASK to return the unshifted field value matching\n> > the function specification.\n> > \n> > While this change appears to be a no-op within tph.c, the external caller\n> > mlx5_st_create() relies on the documented function behavior, making this\n> > fix necessary.\n> \n> Previously, pcie_tph_get_st_table_loc() returned 0x0 (for\n> PCI_TPH_LOC_NONE), 0x2 (for PCI_TPH_LOC_CAP), or 0x4 (for\n> PCI_TPH_LOC_MSIX).\n> \n> mlx5_st_create() is currently the only external caller. It only\n> checks for PCI_TPH_LOC_NONE, which is 0 regardless of the FIELD_GET(),\n> so I don't think this actually fixes mlx5_st_create().\n> \n> Probably still worth a stable backport because other drivers may call\n> pcie_tph_get_st_table_loc() in the future, and if they depend on\n> PCI_TPH_LOC_CAP or PCI_TPH_LOC_MSIX, and are backported to stable\n> kernels, they will need this.\n> \n> I might reword that last paragraph to avoid the implication that this\n> actually fixes something in mlx5:\n> \n> This doesn't make a difference to mlx5_st_create(), the lone\n> external caller, because it only checks for PCI_TPH_LOC_NONE (0),\n> but will be needed for callers that check for PCI_TPH_LOC_CAP or\n> PCI_TPH_LOC_MSIX.\n\nRight, we are running TPH in mlx5 regression and it works perfectly\nwithout \"the fix\".\n\nThanks","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=K4ZsjtHj;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; 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