Re: [PATCH v9 11/11] PCI/CXL: Restore HDM state after CXL bus reset

[Richard Cheng <icheng@nvidia.com>]

On Thu, Jul 09, 2026 at 01:03:04AM +0800, Srirangan Madhavan wrote:
> CXL bus reset can clear HDM global control and decoder programming. Restore
> cached HDM state after a successful cxl_bus reset while the IOMMU reset block
> remains active.
> 
> This intentionally restores only the HDM component decoder state cached by the
> CXL reset support. It does not attempt to restore CXL Device DVSEC
> range/control registers.
> 
> This was exercised with cxl_bus reset on a CXL Type 2 device. Testing confirmed
> that CXL Device DVSEC range/control state is a separate restore class from HDM
> component decoder state.
> 
> This depends on the CXL reset series because it reuses the HDM state cache and
> restore helper introduced there.
>

Tested-by: Richard Cheng <icheng@nvidia.com>
 
> Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> ---
>  drivers/cxl/core/reset.c | 5 +++++
>  drivers/pci/pci.c        | 3 +++
>  include/cxl/cxl.h        | 6 ++++++
>  3 files changed, 14 insertions(+)
> 
> diff --git a/drivers/cxl/core/reset.c b/drivers/cxl/core/reset.c
> index f708c7b80acf..67cdc51182f7 100644
> --- a/drivers/cxl/core/reset.c
> +++ b/drivers/cxl/core/reset.c
> @@ -894,6 +894,11 @@ static int cxl_restore_hdm_decoders(struct cxl_reset_context *ctx)
>  	return cxl_restore_hdm(ctx->target);
>  }
>  
> +int cxl_restore_hdm_after_pci_reset(struct pci_dev *pdev)
> +{
> +	return cxl_restore_hdm(pdev);
> +}
> +
>  static void cxl_hdm_range_context_init(struct cxl_hdm_range_context *ctx)
>  {
>  	INIT_LIST_HEAD(&ctx->ranges);
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index ef25ba5f7fe9..b394704950a5 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5004,6 +5004,9 @@ static int cxl_reset_bus_function(struct pci_dev *dev, bool probe)
>  		pci_write_config_word(bridge, dvsec + PCI_DVSEC_CXL_PORT_CTL,
>  				      reg);
>  
> +	if (!rc)
> +		rc = cxl_restore_hdm_after_pci_reset(dev);
> +
>  	pci_dev_reset_iommu_done(dev);
>  	return rc;
>  }
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index de58f484b7d9..c1019e1b3b27 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -154,6 +154,7 @@ int cxl_commit(struct cxl_decoder_settings *settings, void __iomem *hdm);
>  #ifdef CONFIG_CXL_HDM
>  void pci_cxl_hdm_init(struct pci_dev *pdev);
>  void pci_cxl_hdm_release(struct pci_dev *pdev);
> +int cxl_restore_hdm_after_pci_reset(struct pci_dev *pdev);
>  int cxl_reset_function(struct pci_dev *pdev, bool probe);
>  #else
>  static inline void pci_cxl_hdm_init(struct pci_dev *pdev)
> @@ -164,6 +165,11 @@ static inline void pci_cxl_hdm_release(struct pci_dev *pdev)
>  {
>  }
>  
> +static inline int cxl_restore_hdm_after_pci_reset(struct pci_dev *pdev)
> +{
> +	return 0;
> +}
> +
>  static inline int cxl_reset_function(struct pci_dev *pdev, bool probe)
>  {
>  	return -ENOTTY;
> -- 
> 2.43.0
>